5,102 research outputs found
Intensity process and compensator: A new filtration expansion approach and the Jeulin--Yor theorem
Let be a continuous-time, time-homogeneous strong Markov
process with possible jumps and let be its first hitting time of a Borel
subset of the state space. Suppose is sampled at random times and suppose
also that has not hit the Borel set by time . What is the intensity
process of based on this information? This question from credit risk
encompasses basic mathematical problems concerning the existence of an
intensity process and filtration expansions, as well as some conceptual issues
for credit risk. By revisiting and extending the famous Jeulin--Yor [Lecture
Notes in Math. 649 (1978) 78--97] result regarding compensators under a general
filtration expansion framework, a novel computation methodology for the
intensity process of a stopping time is proposed. En route, an analogous
characterization result for martingales of Jacod and Skorohod [Lecture Notes in
Math. 1583 (1994) 21--35] under local jumping filtration is derived.Comment: Published in at http://dx.doi.org/10.1214/07-AAP447 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
TopoSZ: Preserving Topology in Error-Bounded Lossy Compression
Existing error-bounded lossy compression techniques control the pointwise
error during compression to guarantee the integrity of the decompressed data.
However, they typically do not explicitly preserve the topological features in
data. When performing post hoc analysis with decompressed data using
topological methods, preserving topology in the compression process to obtain
topologically consistent and correct scientific insights is desirable. In this
paper, we introduce TopoSZ, an error-bounded lossy compression method that
preserves the topological features in 2D and 3D scalar fields. Specifically, we
aim to preserve the types and locations of local extrema as well as the level
set relations among critical points captured by contour trees in the
decompressed data. The main idea is to derive topological constraints from
contour-tree-induced segmentation from the data domain, and incorporate such
constraints with a customized error-controlled quantization strategy from the
classic SZ compressor.Our method allows users to control the pointwise error
and the loss of topological features during the compression process with a
global error bound and a persistence threshold
5 GHz TMRT observations of 71 pulsars
We present integrated pulse profiles at 5~GHz for 71 pulsars, including eight
millisecond pulsars (MSPs), obtained using the Shanghai Tian Ma Radio Telescope
(TMRT). Mean flux densities and pulse widths are measured. For 19 normal
pulsars and one MSP, these are the first detections at 5~GHz and for a further
19, including five MPSs, the profiles have a better signal-to-noise ratio than
previous observations. Mean flux density spectra between 400~MHz and 9~GHz are
presented for 27 pulsars and correlations of power-law spectral index are found
with characteristic age, radio pseudo-luminosity and spin-down luminosity. Mode
changing was detected in five pulsars. The separation between the main pulse
and interpulse is shown to be frequency independent for six pulsars but a
frequency dependence of the relative intensity of the main pulse and interpulse
is found. The frequency dependence of component separations is investigated for
20 pulsars and three groups are found: in seven cases the separation between
the outmost leading and trailing components decreases with frequency, roughly
in agreement with radius-to-frequency mapping; in eleven cases the separation
is nearly constant; in the remain two cases the separation between the outmost
components increases with frequency. We obtain the correlations of pulse widths
with pulsar period and estimate the core widths of 23 multi-component profiles
and conal widths of 17 multi-component profiles at 5.0~GHz using Gaussian
fitting and discuss the width-period relationship at 5~GHz compared with the
results at at 1.0~GHz and 8.6~GHz.Comment: 46 pages, 14 figures, 8 Tables, accepted by Ap
The Impact of Different Herdsmen’s Size on Grassland Ecosystem of Eastern Transect in Tibetan Plateau: A Case Study from Maqu
In order to address grassland degradation, an individual contracting system, or namely, single-household rangeland management, based on Garrett Hardin theory of “tragedy of the commons”, had been conducted in Maqu since 1980s. Despite the support of local government, such a well-intentioned system saw little fruits on managing degradation, encountering extensive frustration due to its poor practical outcomes. Meanwhile, joint-household rangeland management, as an inheritance of locality-based management, has been vigorously pursued and has played an important role on Maqu’s grassland management system. In order to better illustrate the impact of size on managing the grassland ecosystem, an experiment was set up in which different herdsmen’s scales (single household, small-scale, medium-scale, large-scale, oversized-scale) existing in Maqu grassland was conducted.
This study was an attempt to provide a groundbreaking management model, thus inspiring the policy-makers to achieve better solutions
Role of extracellular signal-regulated kinase 1/2 signaling underlying cardiac hypertrophy
Cardiac hypertrophy is the result of increased myocardial cell size responding to an increased workload and developmental signals. These extrinsic and intrinsic stimuli as key drivers of cardiac hypertrophy have spurred efforts to target their associated signaling pathways. The extracellular signal-regulated kinases 1/2 (ERK1/2), as an essential member of mitogen-activated protein kinases (MAPKs), has been widely recognized for promoting cardiac growth. Several modified transgenic mouse models have been generated through either affecting the upstream kinase to change ERK1/2 activity, manipulating the direct role of ERK1/2 in the heart, or targeting phosphatases or MAPK scaffold proteins to alter total ERK1/2 activity in response to an increased workload. Using these models, both regulation of the upstream events and modulation of each isoform and indirect effector could provide important insights into how ERK1/2 modulates cardiomyocyte biology. Furthermore, a plethora of compounds, inhibitors, and regulators have emerged in consideration of ERK, or its MAPK kinases, are possible therapeutic targets against cardiac hypertrophic diseases. Herein, is a review of the available evidence regarding the exact role of ERK1/2 in regulating cardiac hypertrophy and a discussion of pharmacological strategy for treatment of cardiac hypertrophy
- …